I'm sorry if this seems like gender stereotyping, it isn't, but it is based on observation.
I've worked with a lot of women in my life, at one time being a supervisor over 20. One thing always seemed to stick out, they would be friendly in front of each other, then as soon as one went away, those remaining would gossip about the other. One of the favourites was, praising, say, new clothes, then criticising it when the wearer left. I think it must just be a trait of women?